• The Journal of the Acoustical Society of Korea
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• v.39 no.1
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• pp.8-15
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• 2020

In this paper, we propose a frame synchronization algorithm for robust to the combined effects of large Doppler fluctuations and extended, time-varying multipath in the underwater acoustic communication. From the algorithm, we can recover a high timing error which is occurred from an acoustic propagation delay and uncertainty of oscillator between transmitter and receiver. In order to verify the performance of the synchronization algorithm, the lake trial results are used. The lake experiments are performed in a Gyeongcheonho located in Mungyeong-si, Gyeongsangbuk-do. We can see that the start position of frame is adjusted after the frame synchronization while the receiver moving.

• Journal of Korea Water Resources Association
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• v.51 no.2
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• pp.109-120
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• 2018

In this study, we conducted flume experiments to investigate the three-dimensional flow structures around a half-submerged spur dike in a straight open channel flume. The experiments were carried out under the two different Froude numbers, 0.10 and 0.18. The results were compared with the previous experimental result conducted for non-submerged spur dike. Three-dimensional instantaneous velocities were measured using Acoustic Doppler Velocimetry (ADV) and water elevation data were collected using ultra sonic distance sensor. The results show that submergence conditions of the spur dike largely influence the three-dimensional flow structures around a spur dike.

• The Journal of Korean Physical Therapy
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• v.17 no.2
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• pp.126-147
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• 2005

TCD(transcranial doppler, TCD) units is a equipment that measure a blood flow velocity in the middle cerebral artery(MCA), anterior cerebral artery(ACA), posterior cerebral artery(PCA), and vertebral artery(VA). The aim of this study was to determine the influence on cerebral blood flow velocity according to different stimulation frequency of interferential currents. 50 patients who has a cervical pain were participated in this study and randomly divided into one of the three experimental, placebo, and control group: (1)IFS 1; $10{\sim}30Hz$ was applied, (2)IFS 2; $30{\sim}50Hz$ was applied, (3)IFS 3; $50{\sim}100Hz$ was applied, (4)placebo; suction only applied, and (5)control; neither suction nor interferential stimulation applied. In the IFS groups, interferential stimulations were applied through four suction electrodes application from the 5th cervical to the 1st thoracic level. The results were as follow; 1. MCA was statistically significant with IFS 1, IFS 2, IFS 3, and Placebo group(p<0.05), But there was no statistical significance between IFS 1 and IFS 3 group(p>0.05). 2. ACA was statistically significant with IFS 1, IFS 2, and IFS 3 group(p<0.05). And IFS 1 was more statistical significance than IFS 3 group on ACA(p<0.05). 3. PCA was statistically significant with IFS 1, IFS 2, and IFS 3 group(p<0.05). And IFS 1 was more statistical significance than IFS 3 group on PCA(p<0.05). 4. VA was statistically significant with IFS 1, IFS 2, and IFS 3 group(p<0.05). And IFS 1 was more statistical significance than IFS 3 group on VA(p<0.05).

• Archives of Plastic Surgery
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• v.45 no.5
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• pp.403-410
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• 2018

Background Radiation-induced skin injury is a dose-limiting complication of radiotherapy. To investigate this problem and to develop a framework for making decisions on treatment and dose prescription, a murine model of radiation-induced skin injury was developed. Methods The dorsal skin of the mice was isolated, and irradiation was applied at single doses of 15, 30, and 50 Gy. The mice were followed for 12 weeks with serial photography and laser Doppler analysis. Sequential skin biopsy samples were obtained and subjected to a histological analysis, immunostaining against transforming growth factor beta (TGF-${\beta}$), and Western blotting with Wnt-3 and ${\beta}$-catenin. Increases in the levels of TGF-${\beta}$, Wnt, and ${\beta}$-catenin were detected after irradiation. Results All tested radiation doses caused progressive dermal thickening and fibrosis. The cause of this process, however, may not be radiation alone, as the natural course of wound healing may elicit a similar response. The latent appearance of molecular and histological markers that induce fibrosis in the 15 Gy group without causing apparent gross skin injuries indicates that 15 Gy is an appropriate dose for characterizing the effects of chronic irradiation alone. Thus, this model best mimics the patterns of injury that occur in human subjects. Conclusions This animal model can be used to elucidate the gross and molecular changes that occur in radiation-induced skin injury and provides an effective platform for studying this adverse effect without complicating the process of wound healing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.419-425
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• 2001

In land mobile communications, multipath fading is one of the key factors which affect the system performance. Some extensive studies have been carried out to improve the degraded performance under this fading channels. The PSAM channel compensation method using channel fading estimation is widely used and TCM is a combined coding and modulation technique that has been shown to provide significant coding gain without increasing the transmission bandwidth. In this paper, we analyze the performance of PSA-TC-8PSK which combines PSAM and TCM over frequency nonselective fading channels. To estimate channel fading, Wiener filter which minimizes error variance is used as compensation method and we analyze the affects on the system performance of the number of filter taps, period of the pilot symbol frame, and the Doppler frequency. In addition, we consider the symbol timing recovery circuit which can be implemented in the full-digital method and analyze the effects of symbol timing error on the system performance.

• Safety and Health at Work
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• v.6 no.3
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• pp.256-262
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• 2015

Background: Heart attack is the most common cause of line-of-duty death in the fire service. Daily aspirin therapy is a preventative measure used to reduce the morbidity of heart attacks but may decrease the ability to dissipate heat by reducing skin blood flow. Methods: In this double-blind, placebo-controlled, crossover study, firefighters were randomized to receive 14 days of therapy (81-mg aspirin or placebo) before performing treadmill exercise in thermal-protective clothing in a hot room [$38.8{\pm}2.1^{\circ}C$, $24.9{\pm}9.1%$ relative humidity (RH)]. Three weeks without therapy was provided before crossing to the other arm. Firefighters completed a baseline skin blood-flow assessment via laser Doppler flowmetry; skin was heated to $44^{\circ}C$ to achieve maximal cutaneous vasodilation. Skin blood flow was measured before and after exercise in a hot room, and at 0 minutes, 10 minutes, 20 minutes, and 30 minutes of recovery under temperature conditions ($25.3{\pm}1.2^{\circ}C$, $40.3{\pm}13.7%\;RH$). Platelet clotting time was assessed before drug administration, and before and after exercise. Results: Fifteen firefighters completed the study. Aspirin increased clotting time before and after exercise compared with placebo (p = 0.003). There were no differences in absolute skin blood flow between groups (p = 0.35). Following exercise, cutaneous vascular conductance (CVC) was $85{\pm}42%$ of maximum in the aspirin and $76{\pm}37%$ in the placebo groups. The percentage of maximal CVC did not differ by treatment before or after recovery. Neither maximal core body temperature nor heart rate responses to exercise differed between trials. Conclusion: There were no differences in skin blood flow during uncompensable heat stress following exercise after aspirin or placebo therapy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.410-418
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• 2017

Results of an analysis of the continuous motion effect for FMCW-SAR system and a signal processing to correct it are presented in this paper. SAR images reconstructed by back-projection algorithm are included as well. To analyze how platform velocity and sampling frequency affect the continuous motion effect, FMCW signal model was used, and the signal processing in time-doppler(t, $k_u$) domain was adopted. Then, back-projection algorithm and modified matched-filter was used to reconstruct SAR images, and it was validated using measured data by airborne FMCW-SAR system in X-band frequency.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.1-10
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• 2002

Hull-propeller-rudder interactions are studied by the iterative computational procedures. Hull effects on the propeller are reflected through the effective velocities computed by the vortex ring method which used the measured nominal wake as input data. A potential based panel method has been developed to solve the propeller-rudder interactions using the obtained effective velocities. Steady flow characteristics around the rudder surface can be obtained by computing the induced velocities on the rudder by the propeller and vice versa are computed by the iterative manner until the converged solutions are obtained. Flow characteristics around the propeller and the rudder are measured by Laser Doppler Velocimetry(L.D.V.) in large cavitation tunnel at Samsung Heavy industries. The gap flow model is adopted to solve the characteristics of the horn rudder. Numerical results are compared with the experimental values and the computed velocity fields and pressure distributions with rudder angle on the horn rudder surface show good agreement with measured ones in large cavitation tunnel.

• Journal of the East Asian Society of Dietary Life
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• v.15 no.3
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• pp.283-291
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• 2005

This study was penonned to provide basic data that predict the usefulness of Gastrodiae rhizoma as food materials for oriental medicinal cuisine(YakSun). We measured the changes of regional cerebral blood flow(rCBF) and blood pressure(BP) in rats, following the intravenous injection of Gastrodiae rhizoma water extract The measurement was continually monitored by laser-doppler flowmeter and pressure transducer in anesthetized adult Sprague-Dawley rats for about two to two and half hours through the data acquisition system composed of MacLab and Macintosh computer. The results of this experiment were as follows. Gastrodiae rhizoma increased the changes of rCBF in rats significantly. The rCBF of Gastrodiae rhizoma did not change by pretreated propranolol, atropin, methylene blue and indomethacin. But the rCBF of Gastrodiae rhizoma was increased by pretreated L-NNA. Gastrodiae rhizaoma decreased the changes of BP significantly. The BP of Gastrodiae rhizoma did not change by pretreated propranolol, atropin, methylene blue and indomethacin. But the BP of Gastrodiae rhizoma was decreased by pretreated L-NNA. These results indicated that Gastrodiae rhizoma might increase the rCBF and the BP which related to nitric oxide synthesis. Also these results indicate that Gastrodiae rhizoma can be used as a safe and clinically applicable to diet therapy of cerebral cardiovascular disease.

• Archives of Plastic Surgery
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• v.44 no.5
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• pp.370-377
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• 2017

Background Composite grafts are frequently used for facial reconstruction. However, the unpredictability of the results and difficulties with large defects are disadvantages. Adipose-derived stem cells (ADSCs) express several cytokines, and increase the survival of random flaps and fat grafts owing to their angiogenic potential. Methods This study investigated composite graft survival after ADSC injection. Circular chondrocutaneous composite tissues, 2 cm in diameter, from 15 New Zealand white rabbits were used. Thirty ears were randomly divided into 3 groups. In the experimental groups (1 and 2), ADSCs were subcutaneously injected 7 days and immediately before the operation, respectively. Similarly, phosphate-buffered saline was injected in the control group just before surgery in the same manner as in group 2. In all groups, chondrocutaneous composite tissue was elevated, rotated 90 degrees, and repaired in its original position. Skin flow was assessed using laser Doppler 1, 3, 6, 9, and 12 days after surgery. At 1 and 12 days after surgery, the viable area was assessed using digital photography; the rabbits were euthanized, and immunohistochemical staining for CD31 was performed to assess neovascularization. Results The survival of composite grafts increased significantly with the injection of ADSCs (P<0.05). ADSC injection significantly improved neovascularization based on anti-CD31 immunohistochemical analysis and vascular endothelial growth factor expression (P<0.05) in both group 1 and group 2 compared to the control group. No statistically significant differences in graft survival, anti-CD31 neovascularization, or microcirculation were found between groups 1 and 2. Conclusions Treatment with ADSCs improved the composite graft survival, as confirmed by the survival area and histological evaluation. The differences according to the injection timing were not significant.